René Descartes (1596-1650)

René Descartes, the most original philosopher to appear since
Aristotle,
is often considered to be the father of modern philosophy. He was born
on March 31, 1596 in La Haye, France (now called Descartes) to a
well-to-do family.

While his father, a judge, encouraged him to continue in law
after graduating, Descartes preferred instead to "pursue his thoughts",
travel and dedicate his
life to intellectual studies.

René was a strong contributor and significant
presence in the growing intellectual and scientific activity of his
time. As well as being a mathematician, he established himself in
physics as the discoverer of the law of refraction in optics and in philosophy
for his most famous work Meditations on First
Philosophy.

In Meditations on First Philosophy,
he raised problems of such radical skepticism about our knowledge of
the world, that he set the agenda for epistemology (study of origins of
knowledge) for the next 300 years. The only thing we can be certain of,
he suggested, is our own existence.

His famous declaration, 'Cogito ergo sum' - 'I think therefore
I am', is his proof of his own existence as a thinking being and the
starting point for the search of certainty.

Descartes objective in the Meditations
was to structure human knowledge on a solid foundation. In reviewing
his own beliefs, he realized that many were conflicting, others
inconsistent, and some more justified than others. He wanted to assign
order to his jumble of beliefs so that as in the certainty of
mathematics, the justification of one proposition could follow from
another. Where would he start?

Rather
than attempt the next to impossible task of examining and categorizing
each belief, he decided to examine them against a method of doubt. He
would do this by questioning the source of his beliefs and by asking if
it was infallible. If it was not, then it was not reliable for
providing the foundations of knowledge.

He also noted that many of his beliefs derived from his senses
or perception, which of course, could be deceptive and misleading. For
instance, a person could be hallucinating or his senses could be eluded
when looking at a stick that appears bent in a stream. Based on this
observation, he declared that any information obtained from the senses
to be uncertain and fallible and therefore untrustworthy.

The one proposition Descartes did trust, however, was his
ability to think
and reason. He felt that since he is able to think, it must
be the case that he exists. Likewise, he must exist in order to be able
to think. The certainty that he was a thinking being gave Descartes the
basis for establishing his foundation of knowledge.

From this 'Cogito' Descartes developed an argument for the
existence of two distinct substances, one material and one non-material
and thus created the philosophical concept of Cartesian dualism.

In Cartesian dualism the mind and body are two distinct and
different substances. Minds are things which think and bodies are
extended things or space-occupiers. Descartes felt that he could not
doubt that he existed as a thinking substance, yet he could still doubt
that he had a body. It was this point that convinced him that mind
could exist independently of matter.

For Descartes the foundations of knowledge were not confined
to philosophy. Mathematics for him was the model of all knowledge
because its truths were undeniable. He felt that anyone seeking truth
should look for the certainty equal to arithmetical or geometrical
demonstration. Likewise, he relied on the human capacity of reason to
perceive something 'clearly and distinctly' without reference to or
dependence upon sensory experience.

Ultimately Descartes set out to show that not only is genuine
knowledge possible, contrary to what the skeptics put forth, but that
mathematically-based scientific knowledge of the material world is
possible. He also demonstrated that we as humans have the intellectual
ability to reach an understanding of the world as well as the power to
make reasoned judgments about it.